Low fever is mainly seen in two cases: one case, the recovery period of the disease, such as bacterial or fungal infection, after the infection is controlled, the body temperature has not fully returned to normal, but has dropped a lot compared to the highest temperature, this is in the recovery period of the infection, low fever may last for some time. In another case, some diseases are predominantly hypothermic themselves, such as tuberculosis caused by Mycobacterium tuberculosis infection. The main manifestation of tuberculosis is a cough, but some people will have symptoms of tuberculosis toxicity and will have a predominantly afternoon and evening low-grade fever. Lastly, tumor-related fever is related to the absorption of tumor necrotic material.